1. Field of the Invention
This invention relates to a method for removing particles from the filtermatrix of a magnetic separator during the presence of a magnetic field therein, as well as to a magnetic separator. The separator comprises a magnet, an inlet for the material to be filtered, an outlet for cleaned material and a filtermatrix positioned between the input and the output through which the material to be filtered is passed; and which can be cleaned using the method according to this invention.
2. Description of the Prior Art
A method of magnetic separation according to which more magnetic particles are separated from less magnetic particles contained in a fluid medium which is subjected to a magnetic field, is known in itself and e.g. extensively used for cleaning kaolien and metal ore. The filtermatrix material can, e.g. be steelwool and the filtermatrix is placed in an intense magnetic field; the difference in magnetic properties of the particles results in that, dependent upon the field strength, the velocity and viscosity of the fluid and the temperature thereof, certain particles are caught in the filtermatrix and others are not.
This method is e.g. described in IEEE Transactions on Magnetics, Vd. Mag-12, no. 5, September 1976 and in the U.S. Pat. Nos. 3,887,457 and 3,988,240.
With normal magnetic circuits, which dissipate several MW, the generation of a magnetic field strength of up to 2T in a restricted volume is possible. However, certain applications, such as the cleaning of kaolien, catching fly-ash and cleaning metal ores require very high field strength and then superconducting magnets must be used of which the magnetic circuit is cooled with liquid helium.
It is clear that after a certain time of use the filtermatrix is saturated with trapped particles and must be cleaned. However, the structure of known magnetic separators, particularly the magnetic circuit thereof, makes the removal of the filtermatrix and the replacement thereof by a new one during the presence of the magnetic field complicated. When a strong electromagnet, such as a superconducting magnet, is used, the turning off of this magnet, followed by the cleaning of the filtermatrix results in many practical problems. The operation is very timeconsuming; in turning-off a superconducting magnet a considerable amount of helium is lost by evaporation and it requires a considerable amount of energy to bring this helium gas back into the liquid state.